Quick Look is a delightfully simple way to browse the contents of the files on your Mac without launching their parent apps. (Select a file, press the space bar, that's it.) But if you’re looking at, say, a PDF or Word document, Quick Look can frustrate, because it doesn't provide any way to select and copy text; if you find a snippet of text you’d like to copy and paste, you still need to launch the parent app. Unless, that is, you know a secret shared by Keir Thomas (author of the excellent Mac Kung Fu).

To make text selectable in Quick Look previews, you just need to enable a hidden Finder setting. Select and copy the code below, open Terminal (/Applications/Utilities), paste that code at the prompt, then press Return:

Lex uses a MacBook Pro, an iPhone 5, an iPad mini, a Kindle 3, a TiVo HD, and a treadmill desk, and loves them all. His latest book, a children's book parody for adults, is called "The Kid in the Crib." Lex lives in New Jersey with his wife and three young kids.